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Electrical Reference Page

Number of wires allowed in an Electrical box:

Step one: Count the wires inside the box, using the table below

Item Counts as

Each insulated wire 1 Conductor

All cable clamps 1 Conductor

Each support for a light or device 1 Conductor

All un insulated wires 1 Conductor

Each device, switch or outlet 2 Conductor

jumper wire 0 Conductor

Step two: use the chart below to determine the maximum number of conductors allowed per box size and shape.

Number of conductors allowed in a wiring box
			Wire size
Box Size ( Inches)	Box Type	14	12	10	8
4 x 1 ^1/8	Octagonal	6	5	5	5
4 x 1 ^1/2	Octagonal	7	6	6	5
4 x 2 ^1/8	Octagonal	10	9	8	7
4 x 1 ^1/8	Square	10	9	8	6
4 x 1 ^1/2	Square	12	10	9	7
4 x 2 ^1/8	Square	17	15	13	10
4 ^{11/16 X} 1 ^1/4	Square	12	11	10	8
4 ^{11/16 X} 1 ^1/2	Square	14	13	11	9
4 ^{11/16 X} 1 ^1/4	Square	21	18	16	14